Copper Carriers: T1 and T3
The first (and still popular) digital trunk carriers used by the telephone industry are called T-carriers. There are a number of different versions of T-carriers, and the CompTIA Network+ exam expects you to know something about them. Let’s begin with the most common and most basic, the venerable T-carrier level 1(T1).
T1 has several meanings. First, it refers to a high-speed digital networking technology called a T1 connection. Second, the term T1 line refers to the specific, shielded, two-pair cabling that connects the two ends of a T1 connection (Figure 8.12). Two wires are for sending data and two wires are for receiving data. At either end of a T1 line, you’ll find an unassuming box called a channel service unit/digital ...

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